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Monday, August 2, 2010

Acacia is the second largest genus in Australia comprising more than 700 species (Harden 1991; Morrison and Davies 1991) and occurs in almost all habitat types. Species range in size from small shrubs to large trees and are ecologically important as 'pioneer' species where they rapidly establish cover following major natural disturbances such as fire (Christensen et al. 1981). Acacia species are commonly known simply as acacias or as wattles and Acacia pycnantha has been adopted as the Australian national floral emblem. Wattles are frequently grown as ornamentals, some are harvested for timber, while others are a source of gums or bark used in various tanning processes. Like the majority of legumes, acacias utilize rhizobia to fix atmospheric nitrogen in the soil enabling them to grow in relatively poor soils (Harden 1991).

In Australia there are two commonly accepted schools of thought regarding the taxonomy of legumes (order Fabales) and their treatment varies with institution and state. For example, The Flora of Australia (George, 1981) recognizes three distinct families, Mimosaceae, Caesalpiniaceae, and Fabaceae while the Flora of New South Wales (Harden 1991) recognizes a single family, Fabaceae (sometimes still referred to as Leguminosae by some workers) with three subfamilies, Faboideae (or Papilionoideae), Caesalpinioideae, and Mimosoideae. There has also been some debate about the placement of Australian wattles in the genus Acacia. Between 1977 and 1989, Pedley of the Queensland herbarium proposed splitting Acacia into several segregate genera supported by findings of workers in France during the late 1960s and 1970s (Pedley 1987). Pedley also proposed the reinstatement of the genus Racosperma for the majority of Australian wattles. To date, this has not been accepted, based on the argument that the name Racosperma was not validly published in 1835 (Hall and Johnson 1993) and the need for further research into the systematics of this large taxon (Maslin 1989).

Archaeological evidence demonstrates the presence of Aboriginal people in Australia for at least 50000 years (Flood 1990) and during this time there has been considerable change in the spatial distribution of vegetation. This has resulted, not only from a changing climate, but also as a consequence of megaherbivore extinction and Aboriginal burning practices (Flannery 1994). This unnatural, increased fire frequency has favored those species able to cope with such a regime. The proportions of grasses, "pioneer" species, annuals and pyrophilic species have increased compared with fire sensitive taxa (Flannery 1994). Such fire adaptive plants usually produce large quantities of seed and increasing the population size of those plants utilized for their seed will naturally increase the food supply. Aborigines deliberately burnt areas to achieve this aim (Flannery 1994; Latz 1995).

Seeds form a staple food among many indigenous peoples and plants native to Australia are no exception. Of all the plant foods in central Australia, seeds are by far the most important. Seeds are usually high in proteins, carbohydrates, and fats and are easily collected, providing a high energy food for the expenditure of relatively small amounts of energy (Latz 1995). Although Australian plants generally produce small seeds they are produced in large quantities. In arid Australia, seed supply is widely available, somewhat predictable and dependable (Flood 1990). These plant products form the dietary staple in that they represent greater than 50% of the total diet and often would constitute 70% to 80%. Hiatt's data compiled from several sources, and describing the proportions of hunting, gathering and fishing performed by various indigenous peoples, lists three central Australian linguistic groups, the Dieri, Arrernte, and Walpiri (Hiatt 1978). In all three cases, 70% of the diet consists of gatherable foods and 30% from hunting. Women are the sole providers of gatherable foods and men the sole hunters and as such, women provide 70% of the total diet of these people in arid Australia. The northern half of the Northern Territory possesses some 40 species of Acacia and although 19 species are useful to Aboriginal people, only one species, A. difficilis has seed that is eaten (Brock 1988). There are other more readily available carbohydrate sources such as yams that require less preparation.

Many grasses provide large amounts of soft seed and have been heavily utilized as a staple food by Aboriginal people, especially throughout arid and semi-arid Australia. The grain was collected, ground to a flour using millstones and water was added to form a paste which was eaten raw or cooked as a damper (unleavened bread) in the ashes. Particular wattle seed was similarly collected, prepared and eaten throughout central Australia. Although these skills still survive (Nganyintja 1985), the use of processed wheat flour has largely replaced these traditional practices (Bryce 1983). These seed grinding practices appear to be a relatively recent technological development. Archaeological excavations in central Australia at Puntutjarpa date the oldest millstones to 3500 years; at Puritjarra they are present for the last 2000 years and at Intirtekwerle, they constitute 10 percent of the artifacts in the last 700 years of deposits. The stratigraphy at two of these sites suggests a massive build-up in the level of the sandplain, the sediments having originated in the Simpson Desert dunefield. This suggests that sites in central Australia older than 5000 years may be deeply buried (Flood 1990). Furthermore, this indicates that Aboriginal people in central Australia have been grinding grass or wattle seed for no more than 4000 years. There are older sites closer to the coast in semi-arid country where the development of such practices became a possibility as a result of the drier climate and in creasing fire frequency. Archaeological evidence from the earliest of these sites, Lake Mungo, in the Willandra Lakes system in western New South Wales, demonstrates the presence of a seed grinding economy over the last 16000 years (Flood 1990).

Of the sixty or so species of Acacia in central Australia, Latz (1995) states that some 50% were, or still are, eaten by Aboriginal people and it is not only the seed which is consumed. Several species exude an edible sugary gum from wounds in the stem or branches which supplies a source of energy. Others are fed upon by insects which themselves secrete an edible substance while species such as A. kempeana are the host for various edible grubs (Kalotas and Goddard 1985) often referred to by non-Aboriginal people as witchetty grubs.

Not all wattleseed was used for food. Many coastal and some arid species contain toxic compounds. A. longifolia is one of the few species recorded as having been eaten in coastal eastern Australia (Kohen 1992), similarly, Acacia georginae seed reportedly contains sodium fluoroacetate the major constituent of 1080, a widely used rodenticide (P. Latz pers. commun.).

A. ligulata, umbrella bush, is a widespread and common semi-arid species. A. Kalotas (pers. comm. 1994) noted that there are mixed reports of the consumption of this seed. During his research near Warburton (eastern Western Australia_approx. 750 km WSW of Alice Springs) with Ngaanyatjara people in 1981-82, this species was recorded as one, the seed of which was commonly consumed. Anecdotal evidence from Yankunytjatjara speakers (approx. 600 km ESE of Warburton), suggests it was a species only eaten when no other seed was available as it caused hair loss, the hair regrowing sometime later (Kalotas 1985). Pintupi people (approx. 400 km north of Warburton) also say it was regularly consumed but said nothing of hair loss (A. Kalotas pers. commun. 1994). It may be that the alopecia (hair loss) resulted from a combination of factors rather than the action of A. ligulata seed alone. If it was consumed amongst the Yankunytjatjara only when other foods were scarce, then malnourishment may have played a role in the loss of hair. The tropical American legume genera, Leucaena and Mimosa, both closely related to Acacia, cause hair loss, when consumed, as a result of the presence of the amino acid, mimosine (Mabberley 1987; Windholz et al. 1983). When Leucaena was first used as a stock feed in northern Australia it caused problems with cattle. This was remedied when a bacterium was isolated from the gut of cattle in Java and introduced into drinking troughs in Australia (A. Kalotas pers. commun. 1994). It is possible that similar toxic compounds are present in Australian acacias and care needs to be taken in the choice of species and their subsequent screening as a part of any development of a new crop. Brand and Maggiore (1991) state that testing for the presence of toxic compounds is mandatory if these plants are to be developed as new food products. Many legume seeds contain a variety of toxic compounds that are usually denatured by the application of heat. These compounds, if untreated, can disrupt intestinal absorption of nutrients and produce growth retardation (Brand and Maggiore 1991).

Although the main use of wattles is as a food source (Goddard 1992; Kalotas and Goddard 1985; Isaacs 1987; Kean 1991; Kohen 1992; Latz 1982,1995; Meggitt 1962; Tindale 1972) they have a number of other uses. These include provision of shelter (Nganyintj a 1985), preparations used as medicine (Anon. 1993), and the manufacture of various tools, musical instruments and weapons (Meggitt 1962; Moyle 1979; Brokensha 1978). Today they are largely used for artifact manufacture (Brokensha 1978) and more recently in various revegetation practices (Last 1990).

Until the mid 1900s, an apparent lack of collaborative research between anthropologists, botanists and zoologists led to difficulties in understanding Aboriginal natural resource use and management. Little traditional ecological knowledge was recorded, but much attention was paid to recording traditional botanical and zoological nomenclature. Anthropologists such as Meggitt (1962) recorded the use of particular plants or animals and the indigenous names for each, but it appears specimens were not collected for accurate identification by botanists or zoologists at a later date. As Aboriginal languages were oral, there was no standard spelling, and so anthropologists and linguists made attempts at recording such names phonetically. Older texts will spell the languages discussed here as "Alyawara" for Alyawerre; "Anmatjarra" and "Anmadjarra" for Anmatyerre; "Aranda" and "Arunta" for Arrernte; "Bindubi" and "Pintubi" for Pintupi; "Bidjandjara", "Pidjandjara", "Pitjandjara" and "Pitjantjara" for Pitjantjatjara; and "Walbiri" for Walpiri, with many other minor variants. There are several sounds for which there are no English equivalents and although spelling standards were established, they were, at times, inadequate and have been revised several times. Pitjantjatjara, for example, has been written since the early 1940s and despite this being a comparatively recent development, there are still inconsistencies in the way some of the sounds are written (Eckert and Hudson 1988). There are various lists of Aboriginal names for plants and animals which do not necessarily match with currently recorded names and so identifying species from these early records is problematic. We have managed to identify wattles that Meggitt (1962) recorded as being used by Walpiri people by cross referencing modern names and taking into account changes in the spelling conventions of linguists during this time (Table 1).

Table 2 indicates the number of species of acacia used as a seed food by particular language groups and, conversely, the number of language groups utilizing each species, in central Australia. There are many names for particular species in common between languages, the main reason being the linguistic affinities represented in the table. The Alyawarre, Anmatyerre and Arrernte languages all belong to the Arandic group while Pintupi and Pitjantjatjara are of the Western Desert group. The Walpiri is a member of the Ngarrkic Group but even so, Walpiri names for Acacia aneura, A. kempeana, A. murrayana, A. stipuligera and A. tetragonophylla are similar to Pintupi and Pitjantjatjara names. The name for A. coriacea, pangkuna or pungkuna, is common amongst all the languages. A. adsurgens and A. stipuligera are very similar in appearance, as are A. pachyacra and A. murrayana, and bear the same Alyawerre and Pitjantjatjara names, respectively. Although A. macdonelliensis is common throughout central Australia, only the Alyawerre used it, while A. maitlandii is widespread but rare and was never used by the Walpiri (Latz 1995). Of the 30 species and languages listed, both the Arandic and Western Desert groups ate 20 species, while the Ngarrkic group ate 21 species. A. aneura, A. coriacea, A. cuthbertsonii, A. estrophiolata, A. kempeana, A. murrayana, A. tetragonophylla and A. victoriae are the most common and more widespread species and are, therefore, the most widely consumed species. A. victoriae is present throughout the entire area, is common and used by all language groups.

In recent years, there has been an upsurge of interest in novel food products and in particular those products branded as "bushfoods." Bushfoods can be defined as native plant or animal products used by indigenous Australians as either a traditional or contemporary foodstuff. This interest has led to the widespread use of bushfoods in the restaurant industry both in Australia and overseas. In some instances, these products have become souvenir items, marketed as "uniquely Australian cuisine" or as having been "wild collected by Aboriginal people on their traditional homelands, just as they have done so for thousands of years." Some of these products such as emu are now farmed commercially to meet growing demands.

Wattleseed is in high demand for use as a ground product in pastries and breads and also as a flavoring in desserts, especially ice-cream. It is also used to produce a high quality coffee-like beverage. Wattleseed is one bushfood product collected almost exclusively by Aboriginal people from wild populations throughout its natural range. The species most commonly collected is Acacia victoriae Benth. as it is generally regarded as having a superior flavor. A. victoriae is widespread over much of central Australia and fruits during December and January. Yield is unpredictable and is influenced by climatic conditions and, as such, is extremely variable. Wattleseed is not yet grown on a commercial scale and the demand far exceeds the supply. Despite this, small quantities of wattleseed are exported to the U.S., Canada, UK, France, Japan and SE Asia.

Several species of Acacia indigenous to central Australia are planted to revegetate or rehabilitate degraded land predominantly on Aboriginal communities throughout central Australia. Species commonly used throughout Pitjantjatjara Lands include A. victoriae, A. murrayana and A. kempeana (pers. obs. 1995). These are relatively fast growing species adapted to low rainfall and extreme temperatures and are planted to provide windbreaks, reduce erosion and to revegetate damaged sites. As the plants reach maturity they are often used for other purposes such as firewood or artifact manufacture (Last 1990) but less commonly for food. Edible grubs (maku) are extracted from the roots of A. kempeana at any opportunity but seed is not usually collected for food (M. Last pers. commun. 1995). These plants have potential as an informal crop, in that they possess a variety of uses which could form an additional source of seed for the bushfoods industry.

Acacia seeds are highly nutritious and contain 26% protein, 26% available carbohydrate, 32% fiber and 9% fat (Brand and Maggiore 1992). The fat content is higher than most legumes with the aril providing the bulk of fatty acids present. These fatty acids are largely unsaturated which is a distinct health advantage although it presents storage problems as such fats readily oxidize (Brand and Maggiore 1992). The mean total carbohydrate content of 55.8±13.7% is lower than that of lentils, but higher than that of soybeans while the mean fiber content of 32.3±14.3% is higher than that of other legumes such as lentils with a level of 11.7% (Brand and Maggiore 1992). The energy content is high in all species tested, averaging 1480±270 kJ per 100 g. Wattle seeds are low glycaemic index foods. The starch is digested and absorbed very slowly, producing a small, but sustained rise in blood glucose and so delaying the onset of exhaustion in prolonged exercise (Brand and Maggiore 1992).

The research at UWS-Hawkesbury is centered upon two species, Acacia victoriae and A. murrayana F. Muell ex Benth. The main aim is to develop quality plants with higher and more consistent yields and with an ease of cultivation that will allow Aboriginal people in arid areas to cultivate, harvest, process and market wattleseed to the world. In addition to this, we are seeking to gain an understanding of the agronomy of these plants through greenhouse and field trials.

A. murrayana is being studied as it has a very different growth habit to A. victoriae. Unlike A. victoriae, it is a spineless species which is a distinct advantage when harvesting seed by hand. In addition, it has potential for soil stabilization and land rehabilitation projects as it is a species capable of regeneration from its roots. This means it can regenerate vegetatively following fire or clearing. The possibility also exists that if crop yields fall due to senescence, the plants could be cut back to ground level without disturbing the soil and the subsequent regrowth should retain the growth and yield characteristics for which it was originally selected.

Work thus far has been aimed primarily at establishing field trials to examine the variation within these plants and the plants' responses to irrigation and fertilizers. Experiments to determine how the plants respond to nitrogen and potassium fertilization and rhizobial innoculation are also in progress.

There are two field trials planted on campus with another to be located at Umuwa in the Musgrave Ranges of northern South Australia. A visit was made to Umuwa in April 1995 to select a site for planting in collaboration with the Pitjantjatjara community.

Studies concerning floral and fruit development and also pollination are planned. Genetic analysis will be performed as part of the examination of variation within these species.

Acacia seed in Australia was, and in some areas still is, used as a food source by Aboriginal people. It is now popular with the emergence of the bush foods industry as a new product with a variety of culinary applications. Wild populations are harvested for their seed, but the plants have potential as a commercial crop. It is hoped that the production of seed for food use is adopted by Aboriginal communities. Roasted Acacia seeds offer an exciting new flavor for pastries and ice-creams and a caffeine free beverage.

*Funding to establish the trial at Umuwa has been made available from a grant by the University of Technology Sydney-Jumbunna Centre for Australian Indigenous Studies, Education and Research for which we are most grateful. Table 1. Aboriginal names given to Acacia species used by the Walpiri as listed by Meggitt (1962) with nomenclatural additions and corrections (Latz 1995). Species names in bold are those identified and/or corrected by the authors. One species remains unidentified and the identity of Meggitt's "waralga" as A. ligulata is uncertain.

Aboriginal names

Acacia species

Former spellingz

Current spellingy

Usesz

ancistrocarpa

birauru

pirraru

No use recorded

aneura

mandja

manja

Edible seeds; wood for implements

coriacea

bangguna

pangkuna

Edible seeds; wood for implements

dictyophleba

bilbirinba

pilpirrinpa

Leaves used medicinally

estrophiolata

jadanbi

yajarnpi

Wood for implements and sacred objects

farnesiana

budunari

putunarri

No use recorded

kempeana

ngalgiri

ngalkirdi

Edible seeds; trunk harbours witchetty grubs

notabilis syn. pruinocarpax

mandala

marntarla

Edible seeds, gum; wood for implements

dictyophleba

badudu

patutu

Wood for spear shafts

unidentified

bilingarba

No use recorded

adsurgens

budjubanda

puju-parnta

Edible seeds

cowleana

ganalarambi

kanarlarrampi

Wood for spear shafts

aff. aneurax

jabiljaru

yapilyardu

Trunk harbours witchetty grubs

adsurgens or tenuissima

minjana

minyana

Edible seeds; wood for implements

ligulata?

waralga

wardarrka?

No use recorded

spondylophylla

bundalji

puntaltji

Trunk harbours witchetty grubs

tetragonophylla

gurara

kurara

Edible seeds

victoriae

ganabargu

kanaparlku

No use recorded

zMeggitt 1962.yLatz 1982, 1985.xNomenclature based on Latz 1995. Table 2.Acacia species traditionally used as edible seed by various central desert linguistic groups and their traditional names. The names are given only where the species was used for food as determined by Latz (1982, 1995); Goddard (1992); Kalotas and Goddard (1985); Meggitt (1962) and Tindale (1972). The lack of use of an otherwise edible species can be due to the absence of that species within that particular linguistic area and does not necessarily suggest the species was regarded as inedible, toxic or of inferior quality. NIA indicates the species is not in the area. Alternative spellings for Alyawarre (Alyawerr), Anmatyerre (Anmatyerr) and Arrernte words are included for the benefit of readers with limited access to recent Australian linguistic works.